The Collaborative Ocular Melanoma Study is a multicenter, randomized, controlled clinical trial designed to compare the efficacy of enucleation vs. irradiation in the treatment of eyes with choroidal melanoma. Candidates for the study will be newly diagnosed cases with choroidal melanoma in one eye greater than 3 mm in height and up to 18 mm by 8 mm in size and with no evidence of metastatic disease. Informed consent will be obtained from all patients prior to randomization. The outcome of primary interest is death from all causes. Secondary outcomes will include death from cancer, whether metastatic or not, diagnosis of other tumors, and preservation of vision. Complications of irradiation and changes in visual acuity will be documented and monitored carefully throughout follow-up. Standardized clinical and data collection procedures will be employed, and standardized forms will be used in all centers. Central training and certification of all study staff will be required. The study will be conduced in cooperating clinics located throughout the United States. The study will be directed by an Executive Committee consisting of 12 to 15 study investigators and a Steering Committee to deal with day-to-day operational decisions. An independent Data and Safety Monitoring Committee will be responsible for assuring the ethical conduct of the study and for reviewing the accumulating data on a regular basis for evidence of adverse or beneficial effects of therapy.